The objectives of this grant proposal are: (1) To further study the interactions of rat IgE and human IgE with IgE receptors with regard to the specificity and activity of the IgE molecules. IgE, the antibody prominently involved in allergic diseases, will be tested for its binding to human basophils and primate mast cells using a variety of assays for binding. (2) To study rat IgE receptor with regard to structure, heterogeneity, carbohydrate portion, fragments, and an associated macromolecule. IgE receptors, found on basophils and mast cells, mediate immediate hypersensitivity. Receptors will be radiolabeled, purified, and analyzed by gel filtration and SDS-polyacrylamide gel electrophoresis. (3) To characterize Fc receptors of rabbit and mouse macrophages as well as human lymphocytes and neutrophils. Radiolabeled receptors will be purified and analyzed using techniques developed with IgE receptor studies. The broad objective is to better understand the structures and functions of cell surface receptors for immunoglobulins.